Dyeing process

Abstract

In the dyeing process of fibrous materials wherein the materials are contacted with a heated aqueous dye medium, the dye removed and the dyed material rinsed, the improvement wherein the aqueous dye containing medium and preferably the dye containing rinses are sent to a treating zone maintained at a pH of at least 7 and treated with an alkali earth metal hypochlorite such as calcium hypochlorite and aluminum sulfite whereby the treated mixture settles into an upper clear aqueous phase and a bottom colored phase, residual chlorine is removed from the clear aqueous phase and the resulting clear aqueous phase passed in heat exchange relationship to the aqueous dye containing material directed to the treating zone and returning the clear, chlorine-free water to the dyeing operation.

What is claimed is: 
     
       1. In a dyeing process for fibrous materials which comprises contacting in at least one dyeing zone the fibrous material to be dyed with a heated aqueous medium containing a water-soluble or water-dispersible dye for said material, removing said aqueous dye-containing medium from said contacting zone after said dyeing, subjecting said dyed material to at least one water rinse operation, the improvement which comprises passing at least said aqueous dye-containing medium to at least one treating zone, maintaining said aqueous dye-containing medium in said treating zone at a pH of at least 7.0 and thoroughly mixing therewith 1 to 10 parts per million of alkali earth metal hypochlorite, adding to the resulting mixture 1 to 10 parts per million of aluminum sulfate, allowing the resulting mixture to settle and form an upper clear aqueous phase and a bottom phase of colored materials, removing said bottom phase, passing said clear aqueous phase to a heat exchanger means in heat exchange relationship with spent aqueous dye-containing medium from said contacting zone after said dyeing to raise the temperature of the clear aqueous phase, removing said heat exchanged clarified aqueous phase from said heat exchanger means to a residual chlorine removal zone wherein residual chlorine is removed by a method selected from the group consisting of aeration with stirring in the presence of ultra violet light followed by filtration, heating to a temperature of at least 180° F for at least 20 minutes and adding 1 to 10 parts per million of alkali metal thiosulfate, and then reheating and returning the clear, chlorine-free water to said dyeing zone. 
     
     
       2. The process of claim 1 wherein the alkaline earth metal hypochlorite is calcium hypochlorite. 
     
     
       3. The process of claim 1 wherein the aqueous rinses are also passed to the treating zone. 
     
     
       4. The process of claim 1 wherein about 3 to 6 parts per million alkaline earth metal hypochlorite are mixed. 
     
     
       5. The process of claim 1 wherein 6 to 12 parts per million aluminum sulfate are added. 
     
     
       6. The process of claim 1 wherein the pH of the dyeing containing medium in said heating zone is about 7.0 to 8.6. 
     
     
       7. The process of claim 1 wherein the dye is an acid dye. 
     
     
       8. The process of claim 1 wherein the dye is a disperse dye.